Discovery 2. Manual — part 519

COOLING SYSTEM - V8

DESCRIPTION AND OPERATION 26-2-11

Viscous fan operation

A = Cold, B = Hot

1 Drive plate
2 Fan body
3 Clearance
4 Valve plate
5 Valve
6 Bi-metallic coil

7 Fluid seals
8 Ball race
9 Fluid chamber

10 Reservoir
11 Return port

When the engine is off and the fan is not rotating, the silicone fluid stabilises within the fluid chamber and the reservoir.
The fluid levels equalise due to the return port in the valve plate being open between the fluid chamber and the
reservoir. In this condition, when the engine is started, silicone fluid is present in the fluid chamber and causes drag
to occur between the drive plate and the body. This causes the fan to operate initially when the engine is started.

As the fan speed increases, centrifugal force and a scoop formed on the fluid chamber side of the valve plate, pushes
the silicone fluid through the return port in the valve plate into the reservoir. As the fluid chamber empties, the drag
between the drive plate and body is reduced, causing the drive plate to slip. This reduces the rotational speed of the
fan and allows it to 'freewheel'.

When the coolant temperature is low, the heat emitted from the radiator does not affect the bi-metallic coil. The valve
remains closed, preventing fluid escaping from the reservoir into the fluid chamber. In this condition the fan will
'freewheel' at a slow speed.

COOLING SYSTEM - V8

26-2-12 DESCRIPTION AND OPERATION

As the coolant temperature increases, the heat emitted from the radiator causes the bi-metallic coil to tighten. This
movement of the coil moves the valve to which it is attached. The rotation of the valve exposes ports in the valve plate
which allow silicone fluid to spill into the fluid chamber. As the fluid flows into the clearance between the annular
grooves in the drive plate and body, drag is created between the two components. The drag is due to the viscosity
and shear qualities of the silicone fluid and cause the drive plate to rotate the body and fan blades.

As the coolant temperature decreases, the bi-metallic coil expands, rotating the valve and closing off the ports in the
valve plate. When the valve is closed, centrifugal force pushes silicone fluid through the return port, emptying the fluid
chamber. As the fluid chamber empties, the drag between the drive plate and the body is reduced and the body slips
on the drive plate, slowing the rotational speed of the fan.

COOLING SYSTEM - V8

ADJUSTMENTS 26-2-13

ADJUSTMENTS

Drain and refill

$% 26.10.01

WARNING: Since injury such as scalding could
be caused by escaping steam or coolant, do not
remove the filler cap from the coolant expansion
tank while the system is hot.

Drain

1. Visually check engine and cooling system for

signs of coolant leaks.

2. Examine hoses for signs of cracking, distortion

and security of connections.

3. Position drain tray to collect coolant.
4. Remove expansion tank filler cap.

LH side

RH side

5. Remove drain plugs from LH and RH sides of

cylinder block and allow cooling system to
drain.

6. Disconnect bottom hose from radiator and

allow cooling system to drain.

7. Disconnect top hose from thermostat and

position open end of hose below level of
coolant pump inlet, to allow coolant to drain
from the system.

Refill

1. Flush system with water under low pressure.

Do not use water under high pressure as it
could damage the radiator.

2. Apply Loctite 577 to cylinder block drain

plugs.Fit drain plugs to cylinder block and
tighten to 30 Nm (22 lbf.ft).

3. Connect bottom hose to radiator and top hose

to thermostat housing. Secure with hose clips.

4. Prepare coolant to required concentration.

+

CAPACITIES, FLUIDS AND

LUBRICANTS, Anti-Freeze Concentration.

COOLING SYSTEM - V8

26-2-14 ADJUSTMENTS

5. Release top hose from retaining lugs on the fan

cowl, leaving the hose to rest on the lugs.

6. Remove bleed screw from top hose.

l

'A' From 03 MY

l

'B' Up to 03 MY

7. Unclip the bleed hose from the battery box.
8. Remove expansion tank from its mounting

bracket. Slowly fill the expansion tank with
coolant, approx. 4 litres (7 pt).

9. Raise the expansion tank approx. 20 cm (8 in)

vertically, coolant will drain into the system.

10. Refill the coolant expansion tank until a steady

flow of coolant is emitted from the bleed hole.

11. Fit the bleed screw then, with the expansion

tank still raised, continue filling the system until
the coolant level reaches the base of the
expansion tank filler neck.

12. Fit expansion tank filler cap, fit the expansion

tank to its mountings and clip the bleed hose to
the battery box.

13. Refit the top hose into its lugs on the fan cowl.
14. Start and run engine until normal operating

temperature is reached, and check for leaks.

15. Switch off engine and allow to cool.
16. Check for leaks and top-up coolant to cold level

mark on expansion tank